Re: [PATCH v3 4/9] clear the memory to store struct page

[Wen Congyang <wency@cn.fujitsu.com>]

Hi, andrew morton:

This patch has been acked by kosaki motohiro. Is it OK to be merged
into -mm tree?

Thanks
Wen Congyang

At 10/19/2012 02:46 PM, wency@cn.fujitsu.com Wrote:
> From: Wen Congyang <wency@cn.fujitsu.com>
> 
> If sparse memory vmemmap is enabled, we can't free the memory to store
> struct page when a memory device is hotremoved, because we may store
> struct page in the memory to manage the memory which doesn't belong
> to this memory device. When we hotadded this memory device again, we
> will reuse this memory to store struct page, and struct page may
> contain some obsolete information, and we will get bad-page state:
> 
> [   59.611278] init_memory_mapping: [mem 0x80000000-0x9fffffff]
> [   59.637836] Built 2 zonelists in Node order, mobility grouping on.  Total pages: 547617
> [   59.638739] Policy zone: Normal
> [   59.650840] BUG: Bad page state in process bash  pfn:9b6dc
> [   59.651124] page:ffffea0002200020 count:0 mapcount:0 mapping:          (null) index:0xfdfdfdfdfdfdfdfd
> [   59.651494] page flags: 0x2fdfdfdfd5df9fd(locked|referenced|uptodate|dirty|lru|active|slab|owner_priv_1|private|private_2|writeback|head|tail|swapcache|reclaim|swapbacked|unevictable|uncached|compound_lock)
> [   59.653604] Modules linked in: netconsole acpiphp pci_hotplug acpi_memhotplug loop kvm_amd kvm microcode tpm_tis tpm tpm_bios evdev psmouse serio_raw i2c_piix4 i2c_core parport_pc parport processor button thermal_sys ext3 jbd mbcache sg sr_mod cdrom ata_generic virtio_net ata_piix virtio_blk libata virtio_pci virtio_ring virtio scsi_mod
> [   59.656998] Pid: 988, comm: bash Not tainted 3.6.0-rc7-guest #12
> [   59.657172] Call Trace:
> [   59.657275]  [<ffffffff810e9b30>] ? bad_page+0xb0/0x100
> [   59.657434]  [<ffffffff810ea4c3>] ? free_pages_prepare+0xb3/0x100
> [   59.657610]  [<ffffffff810ea668>] ? free_hot_cold_page+0x48/0x1a0
> [   59.657787]  [<ffffffff8112cc08>] ? online_pages_range+0x68/0xa0
> [   59.657961]  [<ffffffff8112cba0>] ? __online_page_increment_counters+0x10/0x10
> [   59.658162]  [<ffffffff81045561>] ? walk_system_ram_range+0x101/0x110
> [   59.658346]  [<ffffffff814c4f95>] ? online_pages+0x1a5/0x2b0
> [   59.658515]  [<ffffffff8135663d>] ? __memory_block_change_state+0x20d/0x270
> [   59.658710]  [<ffffffff81356756>] ? store_mem_state+0xb6/0xf0
> [   59.658878]  [<ffffffff8119e482>] ? sysfs_write_file+0xd2/0x160
> [   59.659052]  [<ffffffff8113769a>] ? vfs_write+0xaa/0x160
> [   59.659212]  [<ffffffff81137977>] ? sys_write+0x47/0x90
> [   59.659371]  [<ffffffff814e2f25>] ? async_page_fault+0x25/0x30
> [   59.659543]  [<ffffffff814ea239>] ? system_call_fastpath+0x16/0x1b
> [   59.659720] Disabling lock debugging due to kernel taint
> 
> This patch clears the memory to store struct page to avoid unexpected error.
> 
> CC: David Rientjes <rientjes@google.com>
> CC: Jiang Liu <liuj97@gmail.com>
> Cc: Minchan Kim <minchan.kim@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> Reported-by: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>  mm/sparse.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fac95f2..0021265 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -638,7 +638,6 @@ static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
>  got_map_page:
>  	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
>  got_map_ptr:
> -	memset(ret, 0, memmap_size);
>  
>  	return ret;
>  }
> @@ -760,6 +759,8 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
>  		goto out;
>  	}
>  
> +	memset(memmap, 0, sizeof(struct page) * nr_pages);
> +
>  	ms->section_mem_map |= SECTION_MARKED_PRESENT;
>  
>  	ret = sparse_init_one_section(ms, section_nr, memmap, usemap);

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